Induction of a photostationary ring-opening/closing state of spiropyran monolayers on the semi-metallic Bi(110) surface

TL;DR

This study demonstrates that spiropyran monolayers on Bi(110) surfaces can undergo reversible photoinduced ring-opening and closing, establishing a photostationary state, which is unusual compared to other metal surfaces due to Bi(110)'s semi-metallic nature.

Contribution

It reveals that spiropyran molecules exhibit enhanced photoactivity on Bi(110) surfaces, enabling reversible switching and photostationary states, unlike on typical metal surfaces.

Findings

Spiropyran monolayers isomerize on Bi(110) surface.

Blue light induces bidirectional ring-opening/closing.

Photostationary state achieved at high illumination intensities.

Abstract

Molecular switches on metal surfaces typically show very little photoreactivity. Using scanning tunneling microscopy we show that the ring-opening/-closing switch nitrospiropyran thermally and optically isomerizes to the open merocyanine form on a Bi(110) surface. Irradiation by blue light of a monolayer spiropyran molecules leads to mixed domains of the two isomers. At large illumination intensities a photostationary state is established, indicating the bidirectional ring-opening and closing reaction of these molecules on the bismuth surface. The enhanced photoactivity contrasts with the case of adsorption on other metal surfaces, probably due to the low density of states at the Fermi level of the semi-metallic Bi(110) surface.